Biochemical experiments are proposed to study in detail the biosynthesis of transfer RNA in Escherichia coli by following the fate of specific tRNA precursors through all the nuclease cleavage and enzymatic modification steps which give rise to mature tRNA. A combination of genetic and biochemical experiments is proposed to generate mutants defective in the regulation of tRNA or aminoacyl-tRNA synthetase biosynthesis and to examine the molecular elements of this control.